What principle explains the distribution of species in a chemical reaction at equilibrium?

Le Chatelier's Principle is a fundamental concept that describes how a system at equilibrium responds to changes in concentration, temperature, or pressure. Specifically, it states that if an external change is applied to a system in equilibrium, the system will adjust itself to counteract that change and restore a new equilibrium position. This principle is crucial for understanding how the concentrations of reactants and products shift when conditions change, thus explaining the distribution of species in a chemical reaction at equilibrium.

For example, if the concentration of one of the reactants is increased, the system will respond by shifting toward the products to reduce the concentration of that reactant and re-establish equilibrium. This dynamic response allows for a predictive understanding of how various perturbations can affect the equilibrium state of a chemical reaction.

The other principles mentioned do not directly address the equilibrium distribution of species in a chemical reaction. Gibbs Free Energy relates to the spontaneity of reactions and the stability of states, Raoult's Law deals with vapor pressures in solution, and the Law of Conservation of Mass focuses on the mass balance in chemical reactions. Therefore, Le Chatelier's Principle is the most appropriate choice for explaining how species are distributed at equilibrium.